Knee joints for orthoses, exoskeletons or prostheses have an upper part with an upper connection part and a lower part with a lower connection part, which are articulatedly connected to one another. In general, receptacles for a thigh stump or a thigh rail are arranged on the upper connection part, whereas a lower leg tube or a lower leg rail are arranged on the lower connection part. In the simplest case, the upper part and the lower part are connected pivotably to one another by means of a uniaxial joint.
To be able to satisfy or support different requirements during the different phases of a step or during other movements or actions in a way that is as natural as possible, a resistance device is often provided which provides flexion resistance and extension resistance. The flexion resistance is used for setting how easily the lower part can be swung backwards in relation to the upper part when a force is applied. The extension resistance brakes the forward movement of the lower part and forms, inter alia, an extension limit stop.
DE 10 2008 008 284 A1 has disclosed an orthopedic knee joint with an upper part and with a lower part arranged pivotably thereon, which upper part and lower part are assigned multiple sensors, for example a flexion angle sensor, an acceleration sensor, an inclination sensor and/or a force sensor. The position of the extension limit stop is determined in a manner dependent on the sensor data.
DE 10 2006 021 802 A1 describes control of a passive prosthetic knee joint with adjustable damping in a flexion direction for adaptation of a prosthesis device with top-side connection means and with a connecting element to an artificial foot. The adaptation is made to climbing stairs, wherein a low-moment lifting of the prosthetic foot is detected, and the flexion damping is, in a lifting phase, lowered to below a level suitable for walking on a level surface. The flexion damping may be increased in a manner dependent on the change in the knee angle and in a manner dependent on the axial force acting on the lower leg.
DE 10 2009 052 887 A1 describes, inter alia, a method for controlling an orthotic or prosthetic joint with a resistance device and with sensors, wherein items of state information are provided by means of sensors during the use of the joint. The sensors detect moments or forces, wherein the sensor data of at least two of the determined variables are linked to one another by means of a mathematical operation, and in this way an auxiliary variable is calculated which is used as a basis for the control of the flexion and/or extension resistance.
According to the prior art, for the control of the change in the damping behavior, the sensor data are evaluated quantitatively, that is to say, in general, certain threshold values are predefined, in the case of the attainment or non-attainment of which the actuator is activated or deactivated, such that the resistance device provides an increased or reduced flexion or extension resistance.
DE 10 2008 024 747 A1 and DE 103 51 916 A1 have disclosed further prosthetic knee joints with which a sitting-down movement is possible.
Resistance units with articulation points or mounting points on the upper part and the lower part are necessarily installed with a spacing to the pivot axis, generally behind the pivot axis in a walking direction. The line of action of the force acting on the resistance unit between the upper articulation point and the lower articulation point thus runs with a spacing to the pivot axis in order to be able to convert the rotational movement into a translational movement of the resistance unit. Rotary hydraulic arrangements have no articulation points on the upper part and lower part.
The spacing of the force action line, running within the resistance unit between the articulation points, to the pivot axis is dependent on the knee angle. The length of a line perpendicular to the action line and running through the pivot axis is regarded as the spacing. The spacing simultaneously defines a lever arm, which is dependent on the knee angle.
It is often difficult for patients, during the movement from standing to sitting, to support their body weight using the unaided leg, such that they must often also use their hands for support.